1. Field of the Invention
Embodiments of the present invention generally relate to the design of gas line systems for chemical vapor deposition chambers.
2. Description of the Related Art
Sub-quarter micron multilevel metallization is one of the key technologies for the next generation of very large scale integration (VLSI). The multilevel interconnects that lie at the heart of this technology require planarization of high aspect ratio apertures, including contacts, vias, lines or other features having aperture widths less than 0.25 μm and aperture depths greater than the aperture widths. Reliable formation of these interconnects is very important to the success of VLSI and to the continued effort to increase circuit density and quality on individual substrates and die.
Metal interconnects are typically formed by physical vapor deposition (PVD), chemical vapor deposition (CVD), electrochemical deposition and/or sequential combinations thereof. CVD metal films, such as CVD aluminum films, provide excellent conformal coverage of features. CVD of aluminum films is typically performed with a bubbled precursor which is transported by means of a carrier gas into the reactor via a gas line system. The bubbled precursor is typically directed though a gas distribution assembly including a showerhead and a blocker plate situated near the top of the chamber. The precursor reacts to form a layer of material on the surface of a substrate that is positioned on a substrate support in the chamber.
The bubbled precursor is introduced into the gas distribution assembly from a system of gas lines that connects sources of the precursor gas and carrier gas to the gas distribution assembly. FIG. 1 illustrates a prior art gas line design 500 having flange connectors for connecting gas sources to a CVD chamber. Flange connectors 502 and 521 connect the gas lines to a nitrogen purge gas source 503. Flange connectors 504 and 523 connect the gas lines to a precursor ampoule 505. Flange connectors 506 and 525 connect the gas lines to a CVD chamber 507. Flange connectors 508 and 527 connect the gas lines to a bypass line 509. Flange connectors 510 and 529 connect the gas lines to a pressure gauge 511. The prior art gas line design includes 3 tee-fittings 512 and three shut-off valves 514 that may trap precursors from the gas source such that material is undesirably deposited in the gas line. The prior art gas line design further comprises flange connectors 520, 522, 524, 526, 528, and 530.
The prior art gas line design also includes twenty weldments 516. The weldments typically provide rough surfaces inside the gas lines. Accumulation of aluminum particles on the weldments from aluminum-containing precursors flowed through the gas lines has been observed. The generation of the contaminating particles may be accelerated depending on the choice of the CVD precursor gas. Over time, the accumulation of the particles on the weldment surfaces inside the gas lines can affect the flow of precursors through the gas lines. Also, particles may flake off and be carried downstream to the chamber and cause damage to other chamber components.
Therefore, there remains a need for a method of reducing the formation of contaminating deposits or particles in gas line systems for chemical vapor deposition chambers.